Counterpoise vs ground wire

[K7TV]

This has largely been answered, but perhaps you would like a personal
perspective on the overall antenna choices with a summary of "grounding"
aspects.

 

There is an enormous number of possible antenna designs for portable use,
but the most popular types seem to be the end-fed conductor and the
center-fed conductor. A connection to the actual ground (soil) is not
recommended in any case.

 

I like to think of end-fed conductors as "short" or "long". A "short" one is
one which is fed at or near a current maximum. A quarter wave is one
example, but shorter wires and even somewhat longer ones fall in this
category. A "long" end-fed conductor would be a half-wave, or something a
little shorter, or anything longer.

 

A "short" end-fed conductor is probably the lightest and most convenient
portable antenna. It does need a counterpoise, which is typically a single
wire about 1/8 to 1/4 wavelength long. You place the counterpoise on the
ground, or better, on top of some bushes. You can do the same with the
antenna wire itself, but you will get better results if you have a support
to elevate the far end. A tree is good if there is one available. A light
fiberglass pole is less suitable, as these tend to be very flexible, and the
top bends with the one-sided load. Another approach is to use a stiff
conductor that supports itself. I like my BuddiPole used as a vertical
conductor (with or without any loading coil; don't be afraid to use a
loading coil if you want to; if the radiator is less than 1/4 wavelenght the
tuner in your radio will act as a loading coil anyway.) Any stiff conductor
can be used in the same way.

 

A "long" end-fed conductor also generally needs a counterpoise, and the same
considerations apply, but with some nuances. With the "short" antenna the
maximum antenna current will be at the feedpoint, which means low elevation.
The "long" antenna will have one or more current maxima higher up. I haven't
done side-by-side comparison, or even comparative modelling, but I believe
you can expect better performance when you get the current maximum or maxima
up higher above ground rather than right at the radio. Another nuance: As
the antenna becomes much longer than 1/2 wavelength, it becomes less
desirable to have it oriented vertically if you are interested in dx. A
sloping wire is good. A special case is when the "long" wire is 1/2
wavelength or multiples thereof. You then have a very high feed impedance.
You may then need a special matching unit rather than the standard tuner in
the radio, but otoh the feed current will be very small, and the
counterpoise can probably be shorter than usual.

 

The center-fed radiators don't need a counterpoise, or you can view one half
as the counterpoise. You can get by with one support in the middle, and the
mechanical load is symmetrical, so a very light pole will work for a wire
dipole. With this configuration you won't have a current maximum at ground
level.

 

My personal experience is mostly with "short" wires and center-fed wires or
stiff radiators. All of them work, but I tend to have better results with
the center-feds than the short end-feds. Long end-feds may be the best if
your support can handle the one-sided pull.

 

Erik K7TV

 

>I am putting together a portable QRP kit that I can fly on a plane with me.
Looking at several different antennas.  With being a portable operation,
what has worked best for some of you to ground the radio ?  I am seeing
references to some of the antennas that they need a counterpoise wire.  Is
this in addition to a ground wire ?

 

Ron

KA4KYI

 

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